1. Field of the Invention
The invention relates generally to anti-corrosion fluid additives and, more particularly, but not by way of limitation, it relates to an improved form of composition for preventing corrosion to the metal parts of cooling systems and the like.
2. Description of the Prior Art
The prior art includes numerous types of anti-corrosion composition extending quite far back in the prior art. Some early approaches to radiator coolant additives included compounds which function both in an anti-corrosion and freezing point depressant manner. This teaching is exemplified by an early U.S. Pat. No. 1,405,320 which calls for an alkali metal chromate additive to an aqueous solution coolant. Later developments, as exemplified by U.S. Pat. No. 2,153,961, teach anti-corrosion protection through addition of a selected alkali metal chlorate to the various antifreeze liquids such as monohydric and polyhydric alcohols. In addition, prior inhibitors have utilized additives for specific metals such as nitrate, phosphates, sodium nitrite and related compounds. Later developments bringing environmental considerations negated use of certain additives, i.e., the potential explosivity of chlorates, the carcinogenous nature of nitrites, etc.
Further expansion of the art saw various other forms of anti-corrosive additive. U.S. Pat. No. 3,231,501 provides a composition for treatment of aqueous coolant with addition of borate salts. U.S. Pat. No. 3,639,263 utilized water-dispersable tannin along with specific sulfonate and inorganic metal salts. Thus, there has been prior teaching for a wide range of organic and inorganic materials for corrosion protection of the metal components of heating and cooling systems. Specific additives have been developed for protection of selected metals such as iron, copper, nickel, solder, etc.